diff --git a/pitest-entry/src/main/java/org/pitest/mutationtest/statistics/MutationStatistics.java b/pitest-entry/src/main/java/org/pitest/mutationtest/statistics/MutationStatistics.java
index e2cb02bd5..ef3ffb2a0 100644
--- a/pitest-entry/src/main/java/org/pitest/mutationtest/statistics/MutationStatistics.java
+++ b/pitest-entry/src/main/java/org/pitest/mutationtest/statistics/MutationStatistics.java
@@ -58,8 +58,12 @@ public long getPercentageDetected() {
       return 0;
     }
 
-    return Math.round((100f / getTotalMutations())
-        * getTotalDetectedMutations());
+    if (getTotalMutations() == getTotalDetectedMutations()) {
+      return 100;
+    }
+
+    return Math.min(99, Math.round((100f / getTotalMutations())
+        * getTotalDetectedMutations()));
   }
 
   public void report(final PrintStream out) {
diff --git a/pitest-entry/src/test/java/org/pitest/mutationtest/statistics/MutationStatisticsTest.java b/pitest-entry/src/test/java/org/pitest/mutationtest/statistics/MutationStatisticsTest.java
new file mode 100644
index 000000000..aa11553e9
--- /dev/null
+++ b/pitest-entry/src/test/java/org/pitest/mutationtest/statistics/MutationStatisticsTest.java
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2011 Henry Coles
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and limitations under the License.
+ */
+package org.pitest.mutationtest.statistics;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class MutationStatisticsTest {
+
+  @Test
+  public void shouldNotHaveHundredPercentIfNotAllKilled() {
+    assertEquals(99, new MutationStatistics(null, 2000, 1999, 1).getPercentageDetected());
+  }
+
+  @Test
+  public void shouldHaveHundredPercentIfAllKilled() {
+    assertEquals(100, new MutationStatistics(null, 2000, 2000, 1).getPercentageDetected());
+  }
+
+  @Test
+  public void shouldHaveHundredPercentIfNoMutations() {
+    assertEquals(100, new MutationStatistics(null, 0, 0, 0).getPercentageDetected());
+  }
+
+}